The long term interests of this laboratory are in the immunology and biological properties of carbohydrate antigens and cell surface receptors. The three projects included in this proposal address different aspects of this central theme. The first project concerns the structure and regulation of a family of monoclonal antibodies directed against the 3-fucosyllactosamine (3-FL) epitope, Ga1beta1-4(fucalpha1-3)GlcNAc-R. We have identified two crossreactive idiotopes of these antibodies and demonstrated that the antibodies and idiotopes occur naturally in several inbred strains of mice. We have also obtained sequences of the N- terminal 30-40 amino acids of the heavy and light chains of four monoclonal antibodies against 3-FL. The heavy chains are encoded by group 4 VH genes, which also encode VH regions of antibodies against galactan and levan. Preliminary studies also provide evidence for idiotypic crossreactions among antibodies to 3-FL, galactan and levan. The specific aims of this project are: (1) to determine the structural and genetic basis of anti-3-FL antibody specificity. We will obtain amino acid sequences of the variable domains of heavy and light chains of anti-3-FL antibodies and identify the VH germline genes; and (2) to analyze regulation of the anti-3-FL immune response, with particular emphasis on idiotypic network connections among antibodies directed against 3-FL, levans and galactans. The second project is an analysis of glycosphingolipids (GSLs) of human endothelial (EC) cells. Although the EC surface has been the subject of intensive biochemical investigation, no information has been available about the GSLs of these cells. We are currently completing the identification of the most abundant GSLs of cultured human umbilical vein EC. The specific aims of this project are: (1) to identify changes in cell surface expression of GSLs resulting from activation by IL 1 and gamma interferon; (2) to determine if cell surface GSLs play a role in mediating the adhesion of neutrophils or lymphocytes to activated EC; and (3) to analyze human sera for the presence of autoantibodies against EC GSL antigens. The third project concerns the biochemistry of an unusual autosomal dominant blood group abnormality. The phenotype In(Lu) is characterized by suppressed expression of several blood group antigens. Our recent studies of In(Lu) erythrocytes have revealed new features of this phenotype, including structural abnormalities and defects in cation metabolism. The aim of this project is to identify the abnormality in glycosylation that we believe is the primary defect that underlies the In(Lu) phenotype.